Because of their antiinflamatory effects, glucocorticoids are often used to reduce edema in neurologic tissue and to otherwise mitigate the consequences of neural inflammation. For example, high dose prednisolone treatment has been shown to be an effective therapy for different eye diseases including severe Graves´ Ophthalmopathy and acute optic neuritis. However, contradictory results exists for the influence of high dose prednisolone therapy per se on tissue blood flow. Thus, in the current study, we plan to investigate the effect of high dose, short time therapy with intravenous prednisolone in patients with optic neuritis and severe Graves´ Ophthalmopathy.